The invention relates generally to bicycles and more particularly to bicycles which can be propelled by both foot pedals and hand cranks.
Although bicycles are used throughout the world as a means of transportation, they have become increasingly popular as a means of attaining physical fitness. Consequently, bicycles have become more technologically sophisticated and expensive as a result of efforts to increase their capabilities and energy efficiency. However, the great majority of bicycles in use rely on leg power for propulsion. Many manually driven bicycles have previously been designed for the purpose of providing a bicycle having the inherent advantage of allowing the user to exercise his arms and upper torso as well as his legs. However, such designs have been unsatisfactory and such prior art manually driven bicycles have not enjoyed widespread popularity.
Many prior art manually powered bicycles have sought to capitalize on the pushing and pulling force a cyclist exerts on the handlebars during use. Such prior art bicycles have consequently used a push/pull mechanism integrated in the handlebar assembly to rotate the front wheel. An example of such prior art design is disclosed in U.S. Pat. No. 4,147,370 to Lindsey, Jr. The Lindsey bicycle incorporates a drive sprocket securely connected to the steering head. The drive sprocket is connected to the handlebars by means of a reciprocating connecting rod. Since the driven sprocket has a clutch assembly, the Lindsey bicycle has a pair of biasing springs attached to the connecting rods to prevent the drive sprocket from remaining on its dead center position each 180.degree. of rotation which could otherwise result in a reversal of the direction of rotation of the sprocket at either extreme limit of travel (dead center position) causing a sudden removal of the resistance force of the handlebar and consequent injury to the cyclist. The main disadvantage of such prior art designs, however, is their inherent complexity. The complicated system of levers and linkages can tend to bind and be generally trouble prone as well as very energy inefficient.
Another prior art bicycle using a handlebar drive system is disclosed in U.S. Pat. No. 4,548,420 to Patroni, Jr. The Patroni bicycle is similar to the Lindsey bicycle in that it uses a push-pull lever system to rotate the front wheel. The handlebars are mounted on a yoke which rides on a guide pin at the top of the steering head. The handlebar yoke is connected to a connecting rod which drives the drive sprocket. The motion of the handlebars during rotation of the front wheel is generally that of a figure eight. However, a primary disadvantage of such a prior art design is that some cyclists find such a handlebar motion to be awkward and not conducive to smooth operation of the bicycle. In addition, this somewhat complicated system of levers and linkages may tend to bind (just as with the Lindsey bicycle) and its many connection points result in excessive frictional energy losses thereby reducing the energy efficiency of the bicycle. Moreover, the frequent change in directional motion of the torso necessitated by the particular type of front wheel drive operation makes it more difficult for the user to steer the bicycle.
Another prior art manual drive bicycle incorporates a manual drive mechanism in addition to a conventional steering assembly. Such a prior art bicycle is disclosed in U.S. Pat. No. 3,823,959 to Winters. The Winters bicycle has a conventional handlebar assembly mounted on the steering head while a separate manual operating assembly for the front wheel drive assembly is also mounted on the steering head behind the handlebars. Consequently, if a cyclist is using both hands to manually drive the bicycle, he cannot properly steer the bicycle because his hands are on the crank handles. If he uses one hand to steer the vehicle and the other hand to manually power the vehicle, he is somewhat off balance and in an awkward position and cannot either manually drive or steer the vehicle very well. Thus, separation of the steering system and manual drive system results in the bicycle being difficult to use.
Other prior art bicycles have sought to enhance the manual driving and maneuvering capabilities of such bicycles by integrating the manual drive and steering assemblies. One example of such a prior art bicycle is disclosed in U.S. Pat. No. 484,712 to Hartley. The Hartley bicycle uses a chain drive system having a drive sprocket mounted on the steering head. The handlebars are journaled in the drive sprocket so that the handlebars may also be used as cranks to rotate the drive sprocket. However, since the chain extends alongside the front forks, turning the handlebars sharpely to the right will cause the chain to contact the bicycle frame. This severely limits the steering capability of the bicycle and consequently the user's ability to maneuver the bicycle.
Other prior art bicycle designs using integral manual drive and steering systems have sought to obviate the steering capability limitations of such designs by repositioning these systems and changing the bicycle's structure. An example of such a prior art bicycle is disclosed in U.S. Pat. No. 3,485,508 to Hudnall. In the Hudnall bicycle, the drive sprocket, hand crank and handlebars are mounted on an extension member which is securely attached to the top of the front fork journal. This positions the drive sprocket, hand crank and handlebars well forward of the front forks. In addition, the front fork journal is elongated so that it extends much higher than the steering sleeve reducing any interference between the manual drive system and the frame. However, an important disadvantage with this type of bicycle is that the hand crank assembly is positioned too far forward for effective use of the cyclist's arms and upper torso body weight in manually driving the bicycle. Moreover, positioning the manual drive assembly so far forward also moves the center of gravity (or balance) of the bicycle and rider combination thereby adversely affecting maneuverability and operability of the bicycle.
A manually driven bicycle is thus needed that will provide proper manual drive and steering capabilities while having a desired center of gravity location so that the bicycle retains desired handling and operability attributes.